1. Field of the Invention
The present invention relates to a teaching position correcting apparatus and a teaching position correction method for correcting positions of plural teaching points in an operation program of a robot.
2. Description of the Related Art
When a relative position or a posture, between a robot and a workpiece, changes due to a change in a set position of the robot or the workpiece, the teaching position of the robot operation program, which is already prepared, must be corrected. This correction operation is particularly necessary when the robot and a relevant facility are transported to an overseas plant, after the robot operation is confirmed following the setting of the robot and teaching of the robot operation in Japan. Further, even when the robot is moved from a certain position to another position within the same plant, this correction operation is also necessary.
An operation program prepared by an offline program also needs to be corrected in the field so that positions of teaching points (teaching point positions) of the robot operation program prepared offline are matched with an actual set position of a workpiece, using an error between the positions of the robot and the workpiece set in the offline and the positions of the robot and the workpiece actually set.
Teaching point data of the robot program usually includes information of a position and a posture of a work tool. Correction of a teaching point includes correction of either one of or both a position of a teaching point and a posture in an existing program.
The teaching point correction operation in a robot operation program is carried out by playing-back a taught robot program at each teaching point at steps at a low speed while confirming the position of each teaching point. Specifically, the robot is stopped immediately before a teaching point in such a manner that the robot or a work tool of the robot is not brought into contact with the workpiece. Next, an operator manipulates a button of a teaching console to move the robot by jog feeding. With this arrangement, the position and the posture of the robot are corrected to match a desired position and a desired posture. The operator manually carries out this correction operation of a teaching point in the robot program. Therefore, considerable amount of time is necessary for this operation. In order to improve the efficiency of the correction operation, various methods have been conventionally proposed.
In Japanese Unexamined Patent Publication No. 4-255003, for example, a robot touches (touches up) three or four predetermined points of a workpiece. In other words, the operator manually moves the robot to match a tool front end of the robot with these predetermined points. Disposition data of the workpiece is calculated from the obtained three or four position data, and the operation program is corrected based on a difference between the disposition data and disposition data obtained offline.
However, according to a method disclosed in Japanese Unexamined Patent Publication No. 4-255003, the robot needs to be manually moved to carry out a touch up operation at plural positions. Therefore, additional time is necessary to carry out the touch up operation. Even when a slight error is present at a position of the front end of the tool of the robot, precision of the correction operation decreases. Further, when a distribution of plural predetermined points for touch up operation is not suitable, disposition data of the workpiece cannot be calculated accurately. Thus, precision of the correction operation also decreases in this case.
To cope with this situation, Japanese Unexamined Patent Publication No. 2004-280529 and a Japanese Unexamined Patent Publication No. 2005-66797 disclose other methods which do not require a touch up operation. These methods disclosed in Japanese Unexamined Patent Publication No. 2004-280529 and Japanese Unexamined Patent Publication No. 2005-66797 are to calculate a position correction amount for a certain teaching point and automatically correct positions of other teaching points based on this position correction amount.
However, in executing the methods disclosed in Japanese Unexamined Patent Publication No. 2004-280529 and Japanese Unexamined Patent Publication No. 2005-66797, it is necessary that a posture change is small and teaching points are continuous. When a posture change is relatively large, the method disclosed in Japanese Unexamined Patent Publication No. 2004-280529 and Japanese Unexamined Patent Publication No. 2005-66797 cannot be used. In order to obtain a position correction amount from one teaching point, a position and a posture of the tool need to be set accurately. However, in actual practice, there is a limit to the operator accurately and visually setting a position and a posture of the tool.
Further, according to the methods disclosed in Japanese Unexamined Patent Publication No. 2004-280529 and Japanese Unexamined Patent Publication No. 2005-66797, when correcting plural programs to carry out operation to the workpiece at the same position, similar correction operation needs to be carried out to these programs.
The present invention has been made in the light of the above problems. It is an object of the present invention to provide a teaching position correcting apparatus and a teaching position correction method capable of accurately correcting positions of teaching points in a robot program in short time.